Approximately 10% of the US population will develop a thyroid nodule that requires clinical evaluation during their lifetime. Although fine needle aspiration (FNA) biopsy has improved the management of thyroid nodules, it may be nondiagnostic, or show indeterminate and suspicious cytologic features in up to 30% of cases. Because the risk of thyroid cancer is anywhere from 10% to 40% in patients with indeterminate and suspicious FNA biopsy results, investigators have evaluated preoperative clinical, imaging and cytologic factors to better predict the risk of thyroid cancer. Unfortunately, none of these factors are accurate enough to determine which patients with suspicious or indeterminate FNA cytologic findings should undergo thyroidectomy. Consequently, all of these patients require a diagnostic thyroidectomy in order to accurately diagnose their disease. Only about 20% of these patients will have a malignant tumor, but those who do will require a completion thyroidectomy. Our long-term goal is to identify diagnostic and prognostic molecular markers of thyroid cancer that would accurately distinguish benign from malignant thyroid nodules, thus eliminating or reducing the need for diagnostic thyroidectomy or completion thyroidectomy and their associated risks and costs. The hypothesis behind the proposed research is that differentially expressed genes can be used to distinguish benign from malignant thyroid nodules, and as markers of disease aggressiveness. This hypothesis is based on our studies of extracellular matrix and adhesion molecules using cDNA array expression analysis in benign and malignant thyroid neoplasms. First, we have found that the level of extracellular matrix protein 1 (ECM1) and transmembrane protease, serine 4 (TMPRSS4) mRNA expression are accurate diagnostic markers for distinguishing malignant from benign thyroid neoplasm. Second, the level of ECM1 mRNA expression also correlated with the extent of disease. Based on these observations, the experimental focus of this proposal are Aim 1) To evaluate the diagnostic accuracy of ECM1 and TMPRSS4 mRNA expression analysis in FNA biopsy samples of thyroid nodules. Aim 2) To determine if ECM1 is a marker of disease-free survival and cause-specific mortality in patients with differentiated thyroid cancer. We will use these results to design a multicenter clinical trial evaluating the diagnostic and prognostic value of ECM1 and TMPRSS4 expression in patients with thyroid neoplasm. [unreadable] [unreadable] [unreadable]